Here, a concept of a segment for a particular frequency in a transmission channel of digital terrestrial broadcasting ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) is described.
As shown in FIG. 3, in a channel of digital terrestrial broadcasting (13 segments having each 6 MHz in Japan divided into 14 and each 0.5 segment at both ends used as a guard band in the shown example), a one-segment broadcast wave provides broadcasting services by emitting a broadcast wave with broadcast data such as H.264 compressed video information carried by QPSK (Quadrature Phase Shift Keying) of one segment (segment number 0). Receivers of one-segment broadcasting used for broadcasting or the like for portable terminals receive the broadcast wave of the segment number 0 to receive video, audio and data. Each 6 segments (a total of 12 segments) at both sides are used to perform MPEG2 compressed HDTV (High Definition TeleVision: high definition television) broadcasting by 64QAM (Quadrature Amplitude Modulation).
There are also SDTV (Standard Definition TeleVision) educational television broadcasting of 4 segments resulting from dividing 12 segments into three and so-called digital radio broadcasting (digital terrestrial audio broadcasting) of 3 segs (3 segments) having 12 segments divided into four.
Here, a method of broadcasting by a partial segment of the number of all segments in transmission channels of broadcasting such as one-segment broadcasting, four-segment broadcasting and three-segment broadcasting is called as a partial segment broadcasting hereinbelow.
And, the partial segment broadcasting such as one-segment broadcasting is suitable for implementation by an SFN (Single Frequency Network) system and implementation by a broadcasting system (area broadcasting) covering a relatively small area by very small transmission power, and further expansion of use in future is expected.
And, one channel is 6 MHz in Japan, 7 MHz in Brazil, and 8 MHz in Indonesia. Japan also has multimedia broadcasting that gathers much more segments.
JP-A-2010-118903 proposes a broadcasting system that can eliminate or reduce dead zones in the area broadcasting by so-called frequency diversity by simultaneously transmitting a signal with the same content in a possible transmission frequency band part other than a usable transmission frequency band to solve a problem that the dead zones are easily caused in a service area by a broadcasting system (area broadcasting) covering a particular area by very small transmission power by use of a one-segment broadcasting system.
In recent years, similar to the area one segment, it is considered to make effective use of a frequency by allotting a service to one central segment only or to individual segments. And, it is also considered overseas that the central segment only is used so to put the retransmission of television broadcasting into practical use. It is specially considered that a solar battery and a one-segment transmission apparatus are installed in combination in overseas villages where no electricity is available to provide services to areas where television broadcasting is not spread sufficiently. Specifically explaining a summary of the system, it has a structure that the solar battery is charged during the daytime, the one-segment transmission apparatus is operated by the charged power during the night, and a television broadcast received from a satellite is retransmitted in real time, so that the television broadcast is enjoyed.
FIG. 4 is a block diagram showing a configuration of a one-segment retransmission system for conventional satellite broadcasting. A program is transmitted from a television station 1, and television broadcasting waves are transmitted from an antenna 2 to a satellite 3. The received signals are retransmitted to each region by the satellite and received as television broadcasting by a shared receiving antenna 4 and a set-top box 5. Video and audio of the program obtained by the set-top box are input to an encoder 6 and converted into a signal form (broadcasting TS) conforming to the ISDB-T system by a ReMUX 7. The broadcasting TS is modulated by an ISDB-T modulator 8 and allotted to one central segment of the channel. Thus, the retransmission signal modulated to one segment is transmitted to a one-segment receiving terminal of each home or portable terminals via a power amplifier 9 and a transmitting antenna 10.
In a system for performing retransmission of broadcasting in real time by use of a one-segment transmission apparatus, retransmitting time is limited sometimes. For example, a case that the one-segment transmission apparatus is operated by the solar battery is taken as an example. There is considered a method of retransmitting television broadcasting by charging the solar battery in the daytime and using the power charged during the daytime to activate the one-segment transmission apparatus during the night. By such a retransmission system, television broadcasting cannot be watched during the daytime when the solar battery is charged, and a program was missed sometimes.